Intake manifolds may be formed with plastics in an effort to reduce vehicle cost and weight. However, plastic components are less dense than an equivalent metal component, which may lead to certain issues. For example, during vehicle travel, a noise may be generated by an air flow pattern at various throttle valve angles, including but not limited to tip-in or fast opening. The noise may penetrate the plastic passageways and radiate to a driver of the vehicle, resulting in undesirable sounds.
One example approach to reduce this noise is shown by Choi et al. in U.S. Pat. No. 5,722,357. Therein, an air diffuser is located between a throttle body and an intake manifold with radial vanes protruding into an intake path. The air diffuser may disrupt an air flow pattern and reduce noise emanating from the intake manifold.
However, the inventors herein have recognized a disadvantage with prior art noise reduction system for intake air passages. As one example, these noise reduction systems may decrease bulk airflow due to their protrusion into the intake path for a given throttle bore size, which may ultimately decrease an engine power output. Furthermore, such intake systems may have discontinuities so that the system can be packaged into the vehicle. Air flowing around these discontinuities can produce noise due to turbulent intake air flow. This noise can be bothersome to customers. Additionally, while increasing throttle bore may be used to counteract flow restrictions, this may cause still other problems related to not only packaging, but also airflow controllability which can be particularly relevant to idle speed control, air-fuel ratio control, etc.
In one example, the issues described above may be addressed by an intake system comprising a throttle body in an intake passage with a bore having a first radius smaller than a second radius of the intake passage and a noise attenuation device with a plurality of vanes located in the intake passage directly downstream of the throttle body and where a maximum height of the vanes is substantially equal to a difference between the radius. In this way, the vanes may decrease noise while not decreasing bulk airflow.
As one example, the vanes extend inwardly into the intake passage for a predetermined height equal to or less than the difference the first and second radius. The vanes may diffuse and/or redirect air flow that may otherwise impinge onto surfaces of the intake passage and produce an undesired noise. By diffusing the intake flow, the noise may be decreased or prevented such that it may not emanate from the intake passage.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.